Field
The present disclosure relates to telecommunications apparatus and methods. In particular, certain embodiments relate to apparatus and methods for determining the height (i.e. altitude/elevation) of a terminal device operating in a wireless telecommunications system.
Description of Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Mobile communication systems have evolved over the past ten years or so from the GSM System (Global System for Mobile communications) to the 3G system and now include packet data communications as well as circuit switched communications. The third generation partnership project (3GPP) has developed a fourth generation mobile communication system referred to as Long Term Evolution (LTE) in which a core network part has been evolved to form a more simplified architecture based on a merging of components of earlier mobile radio network architectures and a radio access interface which is based on Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) on the uplink. Further developments to LTE-based systems are being made in the context of so-called Long Term Evolution-Advanced (LTE-A) architectures.
Newer generations of mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) (including LTE-A) architectures are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. This has led to the development of terminal devices, such as so-called smart phones, that are able to provide functionality that goes beyond simple voice and messaging services. One aspect of terminal devices that is becoming more and more common is the ability for terminal devices to determine their own location, for example using satellite-based positioning systems, such as the Global Positioning Satellite (GPS) system. Other satellite-based positioning systems could be used, such as the Galileo system and the Global Navigation Satellite System (GLONASS).
There have been proposals to make use of terminal device's ability to establish and report its location for various purposes, for example to help locate a lost telephone or to help emergency responders locate a person needing assistance. With this in mind, in the United States of America the Federal Communications Commission (FCC) has issued a proposal to the mobile industry to seek to provide schemes for locating terminal devices with sufficient accuracy to allow emergency responders to more reliably locate a terminal device in a building (see FCC publication FCC-14-13, Wireless E911 Location Accuracy Requirements, Adopted: Feb. 20, 2014 Released: Feb. 21, 2014—https://apps.fcc.gov/edocs_public/attachmatch/FCC-14-13A1.pdf [1]).
It may be expected existing schemes for determining a terminal device's location, for example using a GPS receiver in the terminal device (potentially with assistance from other positioning technologies, such as Wi-Fi and/or cellular positioning techniques using so-called assisted GPS), may already be able to provide a desired level of positioning accuracy in horizontal dimensions (i.e. to provide a 2D position, e.g. in terms of latitude and longitude). However, it is well recognized that GPS-based receivers are typically less accurate when providing height information. This is basically because a GPS receiver can only receive signals from satellites above the horizon, whereas for each direction in the horizontal plane they can receive signalling from satellites located to both sides of the receiver. Consequently, it can be expected that existing schemes for determining a terminal device's position may be unable to determine the location of a terminal device with sufficient vertical accuracy to allow the floor of a building in which the terminal device is located to be reliably determined. The issue of reduced vertical accuracy as compared to horizontal accuracy is especially significant in the context of seeking to determine on which floor of a building a terminal device is located because GPS-based receivers generally work less well in buildings due to increased signal penetration losses. Furthermore, the consequence of an inaccurate height determination will often be more significant than an inaccurate horizontal position because it will generally take an emergency responder more time to move from one floor to another floor when it is realised there is an error in vertical determination than to move from one room to another room on the same floor when there is an error in horizontal determination.
In view of these issues there is a need for improved schemes for determining the height (vertical location) of a terminal device operating in a wireless telecommunications system.